Difference between M998 and M998A1 & Engines

[Action]

how can i determine if its even an A1? I realize what was changed but not sure how to compare to know exactly what to look for.

Your data plate shows "m998a1". There is the "a1"
Also, your dash may be broken. The lights switch is sticking way out. There should be 4 tabs behind the face of the dash to hold the switch further back...

 

[Retiredwarhorses]

You guys can't get to wrapped up in data plates...you have no idea what was done during reset. im sure a lot of you saw the 2004 m998's with 6.2's in them. If a data plate was removed and re-riveted on, they use the same holes. The trucks have been outside in the wheather for years since reset. Then there is the IROAN process "inspect repair on as need" basis only. If all was ok, it would not get a new motor...I believe A1's had the cast upper spring mount as well.

 

[Retiredwarhorses]

Your data plate shows "m998a1". There is the "a1"
Also, your dash may be broken. The lights switch is sticking way out. There should be 4 tabs behind the face of the dash to hold the switch further back...

Thats becasue the tabs were removed to install a previous electronic light switch most likely....I have a truck here same way.

 

[Retiredwarhorses]

Let me add... I just bought a truck that has no date of delivery....

 

[desmodromic]

That master cylinder only came on A1's and up.

My 1995 A1 with a 6.2 has that master cylinder as well

You guys can't get to wrapped up in data plates...you have no idea what was done during reset. im sure a lot of you saw the 2004 m998's with 6.2's in them. If a data plate was removed and re-riveted on, they use the same holes. The trucks have been outside in the wheather for years since reset. Then there is the IROAN process "inspect repair on as need" basis only. If all was ok, it would not get a new motor...I believe A1's had the cast upper spring mount as well.

Do you by chance have a pic of the cast spring mount? I am curious about exactly what to look for.

Thats becasue the tabs were removed to install a previous electronic light switch most likely....I have a truck here same way.

This is exactly what happened with my 1990. I was excited that it had the electronic switch, but that was soon squashed when I discovered it did not work correctly. Even less thrilled when I realized they had cut off the standoff tabs. I'll have to fab up some spacers to get the new three lever switch positioned correctly.

 

[brazengoat06]

Anyone notice that emissions exemption sticker

 

[brazengoat06]

My 1995 A1 with a 6.2 has that master cylinder as well



Do you by chance have a pic of the cast spring mount? I am curious about exactly what to look for.



This is exactly what happened with my 1990. I was excited that it had the electronic switch, but that was soon squashed when I discovered it did not work correctly. Even less thrilled when I realized they had cut off the standoff tabs. I'll have to fab up some spacers to get the new three lever switch positioned correctly.

So sounds like I'll need to invest in a new electronic switch?

 

[86humv]

So sounds like I'll need to invest in a new electronic switch?

If you want a potential switch fire....and possibly burnt wires......then take a chance.
I just shipped some donor wires and switch connectors to a shop in Az. because of the neat Elect. light switch.
The good'ol lever switch is the way to go.

 

[Action]

Do you by chance have a pic of the cast spring mount? I am curious about exactly what to look for.

There are 4 bolts holding the upper spring perch to the frame rail. Look at the area that the spring touches the mount. If that spot is between the upper and lower bolts, it is cast. The welded version has the coil touching at the bottom of the mount, below all 4 bolts.

 

[Retiredwarhorses]

So sounds like I'll need to invest in a new electronic switch?

the digital light switch is not authorized for use in the HMMWV due to issues pointed out...the 3 lever switch is still standard issue on new HMMWV's.

 

[brazengoat06]

I know the lights work so I'll just tack weld the control to the dash if I have to. I didn't know about the issues with the electronic switch

 

[SSGKING]

"and 1994-2004 that its all 6.5 NA's and Turbos"

From what I have determined, Turbo's did not come off the production line until 1996 and after.

I was a 63B for almost 10 years in the army and have been a 15T (Blackhawk Mechanic) for the last 12. The difference in the 998 and 998A1 is the upgrades. Just like a Blackhawk designation changes from UH-60A to a UH-60A+ simply by upgrading the engines. A M998A1 did have the 6.5L turbo diesel, which was introduced in 1994. However I myself have a M998A1 with the 6.2L diesel in it. This is possible due to the fact that when a military vehicle goes to the auction if the larger/newer engine is still in good operational use the Army will make the determination to change out the engine with an older previous model engine. This is always done on the blackhawks when they go to the auction as well. Even if the engine is swapped out for auction purposes doesn't mean that all of the other modifications that were done to make it an 998A1 were removed. In the case of mine all other mods are still in place except for the upgraded 6.5L engine. Honestly if you have ever dealt with the two engines you will find that the 6.2L is a much better engine. When they swapped my engine out the did just that swap the engine however they left the HO fuel pump in the vehicle which allows my HMMWV to cruise easily down the road at 70+mph.

 

[Retiredwarhorses]

I was a 63B for almost 10 years in the army and have been a 15T (Blackhawk Mechanic) for the last 12. The difference in the 998 and 998A1 is the upgrades. Just like a Blackhawk designation changes from UH-60A to a UH-60A+ simply by upgrading the engines. A M998A1 did have the 6.5L turbo diesel, which was introduced in 1994. However I myself have a M998A1 with the 6.2L diesel in it. This is possible due to the fact that when a military vehicle goes to the auction if the larger/newer engine is still in good operational use the Army will make the determination to change out the engine with an older previous model engine. This is always done on the blackhawks when they go to the auction as well. Even if the engine is swapped out for auction purposes doesn't mean that all of the other modifications that were done to make it an 998A1 were removed. In the case of mine all other mods are still in place except for the upgraded 6.5L engine. Honestly if you have ever dealt with the two engines you will find that the 6.2L is a much better engine. When they swapped my engine out the did just that swap the engine however they left the HO fuel pump in the vehicle which allows my HMMWV to cruise easily down the road at 70+mph.

Ummmm, M998A1's do not and never had turbo motors, Turbo did not come out till M1113 and that was mid 2k.
The 6.2L was mfg discontinued and the 6.5NA was the replacement. The 6.5 as a direct replacement was referred to as
"detuned", production trucks got a slightly different motor with more HP, A2 trucks had an even better 6.5NA Mfg'd by GEP.

 

[papakb]

There was a plate that was part of the M151 ROPS kits that was used to relocate the main light switch because the rollbar would have covered it. If you can find one of those plates remounting the light switch becomes a piece of cake.

 

[Action]

..... A M998A1 did have the 6.5L turbo diesel, which was introduced in 1994. However I myself have a M998A1 with the 6.2L diesel in it. This is possible due to the fact that when a military vehicle goes to the auction if the larger/newer engine is still in good operational use the Army will make the determination to change out the engine with an older previous model engine. ......

So you are saying the military will auction a humvee with a turbo engine, but first they will put in an N/A motor and replace the wiring and other related parts? Lololol

 

[erasedhammer]

I was a 63B for almost 10 years in the army and have been a 15T (Blackhawk Mechanic) for the last 12. The difference in the 998 and 998A1 is the upgrades. Just like a Blackhawk designation changes from UH-60A to a UH-60A+ simply by upgrading the engines. A M998A1 did have the 6.5L turbo diesel, which was introduced in 1994. However I myself have a M998A1 with the 6.2L diesel in it. This is possible due to the fact that when a military vehicle goes to the auction if the larger/newer engine is still in good operational use the Army will make the determination to change out the engine with an older previous model engine. This is always done on the blackhawks when they go to the auction as well. Even if the engine is swapped out for auction purposes doesn't mean that all of the other modifications that were done to make it an 998A1 were removed. In the case of mine all other mods are still in place except for the upgraded 6.5L engine. Honestly if you have ever dealt with the two engines you will find that the 6.2L is a much better engine. When they swapped my engine out the did just that swap the engine however they left the HO fuel pump in the vehicle which allows my HMMWV to cruise easily down the road at 70+mph.

As far as I know all fuel pumps are the same for NAs and turbos. . Are you talking about the injection pump?

 

[86humv]

The H1 hummer first got a turbo in 96, but not Hmmwv's....that was after 2000 , and only on A2's ....M11xx series.

 

[parklandtrans]

M998&m998a1 i.d.

That master cylinder only came on A1's and up.

When it comes to HMMWV's and I.D.ing of parts and components...I have found it to be a very wise decision and considerably less painful to heed the advice and recommendations of Mr.86humv..!!!
Thru his information and advice I have been saved many hours of my time and he has "SAVED ME" a lot of $$$ in the process..as usual " My is off to him"

 

[BLK HMMWV]

Deleted:
My comments really served no useful purpose.

 

[WeekendWarrior]

I have a 1987 M998 that I bought off Govplanet. It has the 6.5 na already installed. It came with the 400 and transfer case uninstalled. What size bolts do I need to bolt the transfer case to the transmission and bolt the transmission/torque converter to the block?

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